f. Summary . The K^ results from the 10 experiments are summarized 

 in Table 3. For the two experiments with a wave period of 3.75 seconds 

 on an initial slope of 0.10 the average K fl was 0.28; the difference 

 between the two experiments was caused by a current pattern which devel- 

 oped only in experiment 72A-06. For the two experiments with a wave 

 period of 2.35 seconds on an initial slope of 0.10 the average K^ was 

 0.125; the difference between the two experiments was caused by a trans- 

 verse wave which occurred only in experiment 72B-10. In the four experi- 

 ments with a wave period of 1.90 seconds on an initial slope of 0.10 the 

 average Kd was 0.08 for each experiment. In the one experiment with 

 a wave period of 1.50 seconds on an initial slope of 0.10, the average 

 K# was 0.05. These results support the following hypothesis: as the 

 wavelength decreases (or the wave steepness increases) on a given initial 

 profile slope, K^ decreases. 



The K^ would then be expected to decrease if the initial profile 

 steepness were decreased for a given wavelength. However, the average 

 Kjj. in the experiment with a wave period 1.90 seconds on an initial 

 slope of 0.05 was 0.12, higher than the four experiments with a wave 

 period of 1.90 seconds on an initial slope of 0.10. 



The effect of the different reflecting processes does not appear to 

 correlate with any change in wave period (or wavelength) . The effect of 

 the steepness of submerged slopes may have been important in all of the 

 experiments, but the correlation between K^, and the offshore slope was 

 much better in the 6- foot tank (Fig. 10). A predominant cause of the 

 variability in experiments 71Y-06 (1.90-second wave), 72D-06 (1.90-second 

 wave; 0.05 initial slope), and 72A-06 (3.75-second wave) was the effect 

 of the elevation at the top of the submerged slope. In all experiments 

 except 72A-10, the foreshore remained fairly stable in shape and the Kp> 

 from the foreshore appeared to have been fairly constant, but in 72A-10 

 the changing foreshore was the predominant cause of K^> variability. 

 The effect of reflection from a plunging breaker appeared to be small 

 and difficult to measure. The increasing width of the inshore shelf 

 (increasing distance between foreshore and offshore) appears to have 

 been a cause of long-term K^, variability in the experiments with the 

 1.90-second wave and the predominant cause of K^ variability in the 

 experiments with the 1.50-second wave (Fig. 11). In the other experi- 

 ments the distance between the foreshore and offshore changed relatively 

 little and K^ variability was shown to be related to other sources. 



3. Variations in Incident Wave Height . 



In the 10 experiments, the measured incident wave (Table 13) was com- 

 posed of the nominal (generated) wave, the re-reflected wave, and, in 

 experiment 72B-10, the transverse wave. Secondary and cross waves were 

 also observed, but they did not affect the measurement of the incident 

 wave height. 



Barnard and Pritchard (1972) state that "Cross waves are standing 

 waves whose crests are at right angles to a wavemaker; they oscillate 



44 



